文献类型：期刊文献

中文题名：位阻和电子效应对位阻型二芳基乙烯光响应性能的影响

英文题名：Steric and Electronic Effects on the Light-Responsive Performance of Sterically-Hindered Diarylethenes

作者：李萌祺[1];张志鹏[1];朱为宏[1]

机构：[1]华东理工大学化学与分子工程学院,精细化工研究所,上海200237

年份：2020

卷号：46

期号：5

起止页码：642

中文期刊名：华东理工大学学报（自然科学版）

外文期刊名：Journal of East China University of Science and Technology

收录：CSTPCD;;Scopus;北大核心:【北大核心2017】；CSCD:【CSCD_E2019_2020】；

基金：国家基金委重点项目(201636002)。

语种：中文

中文关键词：光致变色;二芳基乙烯;位阻效应;量子效率;热稳定性

外文关键词：photochromism;diarylethene;steric-hindrance;quantum yields;thermal stability

摘要：传统二芳基乙烯体系由于平行与反平行构象异构体无法分离,闭环量子效率通常无法超过50%(摩尔分数)。通过增加位阻效应可以有效阻断两个异构体之间的转化,有可能得到较高的闭环量子效率。本文系统地比较了侧端位阻效应,并通过引入供电子的对甲氧基苯基基团和吸电子的吡啶基团,分析了位阻型二芳基乙烯体系光响应性能的影响。研究发现在噻吩β位引入甲基取代基的目标化合物1和3,开环的平行与反平行异构体可成功实现分离,并且两者反平行异构体闭环量子效率均突破传统体系50%(摩尔分数)的限制;但目标化合物1和3对应的闭环体1c和3c,所引入的甲基降低了其热稳定性。与目标化合物1和3产生鲜明对比的是,由于氢原子较小的位阻效应和可能的分子内氢键的作用,目标化合物2c和4c则具有良好的热稳定性。另外,噻吩取代基的电子效应也会影响热稳定性,含有吸电子基团吡啶的目标化合物1c热衰减速率明显高于含供电子基团对甲氧基苯基的化合物3c。
The photocyclization quantum yield of traditional diarylethene systems is always limited to 50%(mole fraction)due to the inseparability of the parallel(p-)and anti-parallel(ap-)conformers.However,it is possible to block the conversion between the two conformers by increasing steric hindrance between the side aryl groups and ethene bridge,thus enhancing the photocyclization quantum yields.Herein,based on the sterically-hindered bisbenzo(thiadizole)ethene bridge,we fully compared the steric effect of side thiophene rings,and got insight into the electronic effects of substitution groups,like the electron-donating,such as anisole unit and the electron-withdrawing pyridine units.The parallel and antiparallel conformers of compounds 1 and 3 can be separated successfully upon introducing the sterically hindered methyl group to theβ-position of thiophene rings,thus greatly improving their photocyclization quantum yields,higher than 50%(mole fraction).Moreover,the incorporated steric hindrance ofβ-methyl groups on thiophene rings results in lower thermal stability of 1c and 3c.In contrast,2c and 4c show good thermal stability which can be attributed to the relatively small steric hindrance and intramolecular hydrogen bond.When compared with the electronic effects,the electron-withdrawing effects of pyridine units brings forth the higher thermal bleaching rate of 1c than that of 3c containing the electron-donating anisole units.